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Zhe Feng, Fengfei Song, Koichi Sakaguchi, and L. Ruby Leung

, baroclinic waves and frontal systems provide strong lifting mechanisms and the Great Plains low-level jet (LLJ) provides anomalous moisture for favorable dynamical and thermodynamical environments for MCS development. In contrast, during summer, favorable environments featuring significantly weaker baroclinic lifting and thermodynamic instability suggest much lower predictability of MCSs compared to spring ( Song et al. 2019 ). Besides limitations in physics parameterizations, it is unclear if GCMs are

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Stephanie A. Henderson, Eric D. Maloney, and Seok-Woo Son

subtropical jet are apparent in most of models shown. The subtropical jet in MRI-CGCM3, GFDL CM3, and MIROC5 extends too far east relative to reanalysis. Furthermore, a southward shift of the jet is apparent in MIROC5. NorESM1-M has the smallest mean zonal wind errors in the Pacific out of the models shown. Fig . 2. Mean 250-hPa zonal wind (contours) for (top left) reanalysis and the good MJO models during DJF. Contours are every 10 m s −1 beginning at 35 m s −1 . Color shading represents the deviation

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Jiabao Wang, Hyemi Kim, Daehyun Kim, Stephanie A. Henderson, Cristiana Stan, and Eric D. Maloney

/phenomena in the tropics (e.g., Neale et al. 2008 ; Lau and Waliser 2011 ; Jin et al. 2013 ; Zhang 2013 ; Kim et al. 2014b ) and the impact extends outside of the tropical region. Anomalous MJO-induced upper-level divergence can generate anomalous Rossby wave source (RWS) by producing divergent flow anomalies in the region of the strong absolute vorticity and its gradient associated with the midlatitude North Pacific westerly jet ( Sardeshmukh and Hoskins 1988 ). Rossby waves excited by the tropical

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Douglas E. Miller and Zhuo Wang

models in recent years exhibit high skill in predicting ENSO from a month to 2 years in advance (e.g., Rosati et al. 1997 ; Jin et al. 2008 ; Luo et al. 2008 ; Kim et al. 2012 ). The NAO is the dominant mode of variability over the North Atlantic, characterized by a seesaw pattern in boreal winter sea level pressure between the Azores high and Icelandic low ( Hurrell et al. 2003 ). Both phases of the NAO are associated with the intensity and structure changes of the midlatitude jet over the North

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Ángel F. Adames and Yi Ming

, with the corresponding increase in height southward toward the Indian Ocean. A low-level westerly jet is seen in the area where the height gradient is strongest. There are also some differences with respect to ERA-Interim. AM4.0 exhibits stronger westerlies that extend farther eastward past the Philippines, and the geopotential height gradient is stronger. The difference in the westerly jet is further shown in Fig. 2 , along with moisture, precipitation, and its variability. Mean precipitation

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Eric D. Maloney, Andrew Gettelman, Yi Ming, J. David Neelin, Daniel Barrie, Annarita Mariotti, C.-C. Chen, Danielle R. B. Coleman, Yi-Hung Kuo, Bohar Singh, H. Annamalai, Alexis Berg, James F. Booth, Suzana J. Camargo, Aiguo Dai, Alex Gonzalez, Jan Hafner, Xianan Jiang, Xianwen Jing, Daehyun Kim, Arun Kumar, Yumin Moon, Catherine M. Naud, Adam H. Sobel, Kentaroh Suzuki, Fuchang Wang, Junhong Wang, Allison A. Wing, Xiaobiao Xu, and Ming Zhao

have important implications for the subseasonal prediction of midlatitude weather extremes (e.g., Henderson et al. 2016 ; Mundhenk et al. 2018 ; Baggett et al. 2017 ). Henderson et al. (2017) developed diagnostics linking teleconnection biases to biases in the position and extent of the North Pacific jet. Figure 2 (from Henderson et al. 2017 ) contains two panels, each having MJO teleconnection performance during December–February on the y axis. In Fig. 2a , the x axis represents an MJO

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Julian F. Quinting and Christian M. Grams

; Methven 2015 ) where it generates anticyclonic PV anomalies (label 3 in Fig. 1 ). When this WCB outflow, along with its diabatically driven divergent flow, impinges on the midlatitude waveguide and jet stream, the waveguide is deflected poleward, and a ridge is built (e.g., Pomroy and Thorpe 2000 ; Grams et al. 2011 ; Teubler and Riemer 2016 ; Bosart et al. 2017 ; Quinting and Reeder 2017 ). This ridge building may trigger the development and downstream propagation of a baroclinic Rossby wave

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James F. Booth, Young-Oh Kwon, Stanley Ko, R. Justin Small, and Rym Msadek

.1175/1520-0469(1987)044<2418:OTROSS>2.0.CO;2 . 10.1175/1520-0469(1987)044<2418:OTROSS>2.0.CO;2 Liu , J.-W. , S.-P. Zhang , and S.-P. Xie , 2013 : Two types of surface wind response to the East China Sea Kuroshio Front . J. Climate , 26 , 8616 – 8627 , doi: 10.1175/JCLI-D-12-00092.1 . 10.1175/JCLI-D-12-00092.1 Liu , T. , and W. Tang , 1996 : Equivalent neutral wind. Jet Propulsion Laboratory Publ. 96-17, 22 pp. Masunaga , R. , H. Nakamura , T. Miyasaka , K. Nishii , and Y. Tanimoto , 2015

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James F. Booth, Catherine M. Naud, and Jeff Willison

. Sprenger , 2016 : On the relationship between extratropical cyclone precipitation and intensity . Geophys. Res. Lett. , 43 , 1752 – 1758 , . 10.1002/2016GL068018 Pithan , F. , T. G. Shepherd , G. Zappa , and I. Sandu , 2016 : Climate model biases in jet streams, blocking and storm tracks resulting from missing orographic drag . Geophys. Res. Lett. , 43 , 7231 – 7240 , . 10.1002/2016GL069551 Rudeva , I

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Motoki Nagura, J. P. McCreary, and H. Annamalai

most of the year, being negative only during March–May and positive during November–December. The map has negative values over the interior of the Arabian Sea, with positive values confined near coasts ( Fig. 5c ), a pattern that reflects the dominance of the southwest monsoon winds in the annual cycle. The bias is largest during the summer ( Fig. 5f ), because the low-level (Findlater) jet in the models is weaker than observed. (iv) Circulation The NAS circulation is complex, with a prominent

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